Insulated glass unit (IGU / sealed double-glazing)

An insulated glass unit (IGU) is two or more panes of glass bonded to a spacer bar around the edge and sealed to trap a dry air or argon-filled gap — the 'sealed unit' that *is* double glazing. The trapped gap, plus the desiccant inside the spacer bar, are what cut heat gain and noise, and their performance is measured by the window's U-value and g-value. The failure mode everyone eventually meets: when the edge seal fails, humid air leaks in, the desiccant saturates, and moisture condenses between the panes — a permanent internal fog or haze you can't wipe off from either side. That's the unmistakable sign the sealed unit (not the whole window) has gone, and the fix is to replace just the glass unit while keeping the existing frame. A low-E coating usually lives on one of the protected internal faces. If a pane has fogged internally, that's a job for glass repair in Dubai — measuring and swapping the failed unit. Fenestration standards bodies such as the FGIA set what these sealed units are built to.